A plurality of sensor signals, formed by sensors of a mobile device carried by a user of the mobile device, such as an accelerometer, a gyroscope, and a magnetometer are used for indoor navigation, e.g., to determine, based on the mobile device's motion linear speed, turning speed, and heading (e.g., direction relative to the magnetic North Pole of the Earth's Magnetic Field), respectively, a current location of the user carrying the mobile device, as the user walks on a given level of a multilevel building. Note that, here, the mobile device's current motion heading is determined from a magnetometer signal, formed by the magnetometer of the mobile device, indicative of magnitude, declination and inclination of Earth's Magnetic Field at an x-y location of the mobile device, e.g., at the current latitude and longitude. Additionally, barometer signals formed by a barometer of the mobile device can be used, in conjunction with other of the noted sensor signals to determine whether the user carrying the mobile device crosses the levels of the building, e.g., while riding in an elevator or climbing up or down a stairwell of the multilevel building.